The question asks to identify the specific instrument used for measuring human body temperature within a narrow range. We need to evaluate each option based on its primary function.
Correct Option: C) Clinical (medical) thermometer is specifically designed for measuring human body temperature within the specified narrow range.
The question asks for an instrument specifically designed to measure very high temperatures in environments where direct contact is impractical or damaging. We need to evaluate each option based on its primary function and temperature measurement capabilities.
Correct Option: A) Pyrometer is specifically designed for non-contact measurement of very high temperatures, making it suitable for applications like furnaces and molten metal.
The question asks about the fundamental physical principle behind the operation of a mercury-in-glass thermometer. We need to identify which property of mercury allows it to measure temperature changes.
D) Thermal expansion (mercury expands or contracts measurably with changes in temperature). This is the correct principle. Mercury has a high coefficient of thermal expansion, meaning it expands and contracts significantly and uniformly over a wide range of temperatures, making it suitable for thermometers. Its expansion is directly proportional to the change in temperature, allowing for accurate calibration.
The question asks why mercury is traditionally preferred for thermometers. We need to evaluate the properties of mercury that make it suitable for this application and compare them with the given options.
A) It has a fairly uniform rate of thermal expansion, does not wet glass, and remains liquid over a wide temperature range. This option accurately lists the key properties that make mercury an excellent choice for thermometers. Its uniform expansion ensures linearity, non-wetting prevents errors, and a wide liquid range allows for broad applicability.
The question asks why alcohol is preferred over mercury in thermometers for very cold environments. This relates to the physical properties of the liquids, specifically their freezing points, which determine their usability across different temperature ranges.
Correct Option: D) Alcohol has a much lower freezing point than mercury, allowing it to remain liquid at extremely cold temperatures
The question asks for the best definition of heat in physics. We need to evaluate each option based on fundamental physics principles related to thermodynamics.
C) A form of energy that flows from a body at higher temperature to a body at lower temperature, when they are in thermal contact.
This definition accurately describes heat in physics. Heat is energy in transit, specifically energy transferred due to a temperature difference. When two bodies at different temperatures are placed in thermal contact, energy (heat) will spontaneously flow from the hotter body to the colder body until thermal equilibrium is reached.